guvna

A simple bit of code to manage the concurrency of a function. Very useful in limiting the number of asynch calls in a loop.

Guvna

Guvna allows for easily managing the number of times a function is run concurrently.

I ran into a problem where I neede to execute a resource intensive function iteratively and quickly killed the box.

To address the problem, I wrote the Guvna to govern the volume and execution of this function.

Added the this.percDone metric to make it easy to show the percentage done in the callback.

Since Guvna now uses integer variables to signal when your callback has completed a run, you MUST include this.next(); in your function, though if you're running an asynch function, you'll likely have to create a reference to this as seen in the example below that gets tucked into the asynch function. In the code below, I call create self so that I can get to the .next() function.

In this example, I use setTimeout to simulate an asynch call.

var response = [],
        Guvna = require('guvna');
 
var guv = new Guvna({
    max: 2,
    list: [ { name: 'blargh' }, { name: 'honk' }, { name: 'toot' } ],
    callbackfunction(l) {
        var rand = Math.floor((Math.random()*10)+1) * 1000,
                self = this;
        setTimeout(function() {
            response.push(l.name+'-'+rand);
            console.log(parseInt(self.percDone*100)+'% complete');
            self.next(); // CHANGE FROM v0.0.1 
        }, rand);
    },
    donefunction() { console.log(response); }
});
 
guv.start();

When declaring your guv variable, you need to pass it several options:

  • list: This is a simple array. Each item in the array is passed to the callback function one at a time.
  • callback: This is the function that you want to govern. It is passed each item from the list.
  • done: This is the function to run when all your callbacks are complete.
  • max: (optional) This is an integer for how many concurrent callbacks you want to have running. Default = list.length
  • 0.0.5 - Added percDone metric.
  • 0.0.4 - Added error handling.
  • 0.0.3 - Tweaked calculation of max if it's omitted.
  • 0.0.2 - Refactored to use tracking variables as using events created unnecessary comnplexity especially when nesting guvnas.
  • 0.0.1 - Initial drop, used events to manage concurrency.